Wax/copolymer composition



United States Patent 3,409,576 WAX/COPOLYMER COMPOSITION Karekin G.Arabian, Walnut Creek, Calif assignor to Shell Oil Company, New York,N.Y., a corporation of Deleware No Drawing. Continuation-impart ofapplication Ser. No. 483,351, Aug. 27, 1965. This application June 27,1966, Ser. No. 560,873

1 Claim. (Cl. 260-285) ABSTRACT OF THE DISCLOSURE Heat scalablepetroleum wax compositions having a viscosity of at least 6000centipoises at 300 F. are obtained by incorporating about 6.5% weight ofethylene/ propylene copolymer of 3.5 intrinsic viscosity and containing85-93 mol percent ethylene units and 6.5% weight of ethylene/vinylacetate copolymer of molecular weight between 25,000 and 90,000 andcomposed of ethylene and vinyl acetate units in a mol ratio of 8:1 to14:1.

This application is a continuation-in-part of Ser. No. 483,351 filedAug. 27, 1965, and now abandoned.

This invention relates to wax-containing coating compositions andparticularly to wax coating compositions containing mixtures ofpolymeric materials, which compositions have physical propertiessuperior to wax coating compositions containing single polymericmaterials.

Petroleum-derived waxes have been used for many years to coat paper andcarton boards especially for use in wrapping and containing dairyproducts and other food products such as bakery goods as well as forcoating cloth, fibers, and food products including cheese and meats torender them moisture-vapor resistant. Such waxes, however, have anunfortunate tendency to crack and peel off the coated articles,especially when they are subjected to repeated flexing or severecreasing. Even waxes modified with polyethylene, while having someimproved properties, show disadvantages relative to brittleness and lackof tensile strength, particularly under low-temperature conditions.

In the last few years, the disadvantages which are normally attendant tothe use of wax in coating applications have resulted in the significantsupplanting of wax alone by the use of polymeric coatings, e.g.,polyethylene in patricular. In addition, polymeric wax reinforcingagents such as copolymers of ethylene and vinyl acetate, have also beenused to some extent in attempting to overcome the inadequacies ofconventional petroleum waxes. Copolymers of ethylene with C olefins havealso been found to have quite excellent wax-reinforcing properties. Inaddition, ethylene-vinyl acrylate copolymers, various synthetic rubbersand the like have been proposed for incorporation into wax.

Most polymer-reinforced waxes or polymers, suitable for coatings, haveconsiderably higher viscosities than the waxes which they are intendedto replace. This means, of course, that the viscosity of the resultingwax-copolymer compositions will increase as the proportion of polymerincreases. Because of the low viscosity levels, i.e., 50 to 300centipoises at 300 R, which are tolerable in conventional coatingequipment, the amount of polymer which can be employed has heretoforebeen severely limited and as a result thereof, only minor improvementsin wax-coating properties have been obtainable. Presently, with thedevelopment of coating machines which are capable of handlingcompositions having much higher viscosities, i.e., in excess of 6,000centipoises at 300 F., highly viscous coating compositions havingsubstantially improved properties can now be exploited. In fact, Wax-"ice coatings containing up to and in excess of 50% of copolymers ofethylene and vinyl acetate have now been disclosed as being useful; seeUS. 3,189,573 issued July 15, 1965. Of course, as the concentration ofpolymer in the coating composition increases, the cost of thecomposition also becomes proportionately greater.

It is, therefore, a principal object of this invention to obtain awax-copolymer composition possessing high viscosity characteristics andrelated desirable physical properties without the associatedprohibitively high cost presently resulting from employingethylene-vinyl acetate copolymer alone in the wax composition. It is afurther object of this invention to combine two ethylene copolymers witha petroleum wax to produce an improved heat scalable coatingcomposition. These objects will be better understood and other objectswill become more apparent from the description of the invention as givenhereinafter.

Now, in accordance with this invention, it has been found that the totalamount of polymer necessary to produce a coating composition withdesirable physical properties including high viscosity, can beunexpectedly reduced by incorporating two types of ethylene copolymers,i.e., ethylene-propylene copolymer (EPC) and a second ethylenecopolymer, rather than a single type of copolymer, with a petroleum wax.More specifically, the ethylene copolymers which can be advantageouslymixed with EPC include the copolymers of ethylene with esters ofterminally unsaturated organic compounds containing 3-5 carbon atoms,preferably selected from the group consisting of esters of terminallyethylenically-unsaturated monocarboxylic acids and saturated aliphaticalcohols and esters of saturated monocarboxylic acids and terminallyethylenically-unsaturated aliphatic alcohols. Examples of suchcomonomers include vinyl acetate, ethyl acrylate and methyl acrylate.

It has been found preferable to employ from 530%, based on total weightof wax and copolymer, of a mixture of ethylene copolymers, and it isespecially desirable to utilize from 10-20% of such a mixture.

The ethylene copolymers of this invention can be employed in amounts offrom 25% to by weight, based on the weight of the total amount ofcopolymers present in the wax-copolymer composition. More specifically,40- 75 as defined above, of the copolymer of ethylene and propylene ishighly advantageous, and especially preferred is 5075%, as definedabove, of the ethylene-propylene copolymer.

It has been found that a viscosity of at least 6,000 centipoises isdesirable for excellent heat scalability and for excellent hot meltstrength (hot tack). As shown in Table I, it is better to blend to about6,000 viscosity, an ethylene/ propylene copolymer of 3.5 intrinsicviscosity (I.V.) as a flexibility improver than to utilize an ethylene/propylene copolymer of 2.5 I.V. and 1.3 I.V. in two respects: (1) a muchlower concentration is needed 7% vs. 22% and 26% (see Examples 1, 2 and3 in Table I), and (2) the flexibility of the blend with 3.5 I.V.ethylene/propylene copolymer is better than the other two. The blenddescribed as Example I in Table I is not acceptable as a commercialblend because of poor adhesion. This defect can be overcome, as shown inExample 5, when 6.5% ethylene/vinyl acetate copolymer is combined with6.5% ethylene/propylene copolymer. The adhesion of the blend is greatlyimproved and a commercially useful blend with around 6,000 c.p.s.viscosity is produced at a total concentration of 13% combinedcopolymers. Example 6 indicates that the same excellent blends cannot bemade by substituting butyl rubber for the ethylene/ propylene copolymerin the three component blend (ethylene/ propylene copolymer, ethylene/vinyl acetate, wax).

TABLE I.SCREENING TESTS WITH ETHYLENE/PROPYLENE COPOLYMERS (EPC) IN WAXBrookfield Adhesion to Mosscote Flexibility of 1-2 mil thick coating,Viscosity Frozen Food Carton Stock, folded at score-line 180 degrees andExample Blend 1 at 300 F. applied at 300 F., air-cooled, stained withIodine solution for 2min.

(cps) stored 24 hours at 77 F.

Folded at 77 F. Folded at 40 F.

1 7.5% Shell EPO (3.5 I.V.) in wax 6, 500 Poor Slight crack on inside;Severe cracks on inside;

no crack on outside. no crack on outside. 2 22% Shell EPC (2.5 I.V.) inwaX 7, 600 do Severe cracks on inside; Severe cracks on inside slightcrack on outand outside. s1 e. 3-....- 26% Shell EPO (1.3 I.V.) in wax7, 600 do Severe cracks on inside Do.

and outside. 4 Commercial blend, 35% ethylene] 6,800 Excellent No crackson inside No cracks on inside and vinyl acetate copolymer (Elvax andoutside. outside. 250) in wax. 5 6.5% Shell EPC (3.5 I.V.) and 0.5% 7,640 do-. do Slight cracks inside Elvex 260 in wax. and outside. 6 6.5%Polyisobutylene-L-80 and 6.5% This blend is so low in blockingtemperature (less than 90 F.) and so poor in Elvax 260 in wax. tensilestrength and scutl resistance that it cannot be considered a suitablecommercial coating.

1 The wax used in all blends is a mixture of Shell Waxes 200:300z400 in30:10:30 ratio.

Table II contains an example which indicates that the same excellentflexibility cannot be obtained where polyethylene is substituted forethylene/propylene copolymer in the three component blend of thisinvention.

TAB LE II Flexibility at 77 F. of 1 mil Coating Folded 180 Degrees on MCorrugated Board and Then Stained.

6.5% Shell EPC (3.5 I.V.) and 6.5% No cracks 011 inside of fold.

Elvax 260 in wax.

6.5% Hercules polyethylene Hitax 1600E, Melt Index=0.22 and 6.5% Elvax260 in wax.

Blend Severe cracks on inside of fold.

The wax used in these experiments is Shell Waxes 2003002100 in 30: 10:30ratios.

The ethylene-vinyl acetate copolymers which are to be used in thecompositions of the invention have a molecular weight up to 100,000 andpreferably between 25,000 and 90,000 and correspond to the generalformula (CH is an unbranched hydrocarbon chain. The average molecularweight of the EPC copolymers may be up to about 5 million; however, itusually varies between about 20,000 and 800,000 and preferably between200,000 and 400,000. Expressed as intrinsic viscosity, copolymerintrinsic viscosities of between about 1.0and 6.0 enhance the physicalproperties of petroleum waxes, providing wax compositions withunexpectedly improved toughness, flexibility, tensile strength,elongation, resistance to cracking at low temperature and otherdesirable properties. Copolymers containing from to moles of ethyleneand from 20 to 5 moles of propylene can be employed in the compositionsof the invention. Preferably, the copolymers are those having between 85to 93 mole percent ethylene and 15 to 7 mole percent propylene. Theintrinsic viscosity of the copolymer is preferably between about 2 and 5and especially between 2.5 and 4.5.

While the process of forming these copolymers does not form a part ofthe present invention, the copolymers may be prepared by well knownprocedures, such as catalytic polymerization. The proportion of catalystshould be'in the order of 0.01-1%, the polymerization being carried outin an inert solvent such as an alkane (cyclohexane). Polymerization inthis manner is normally conducted under low pressures in the order of1-30 p.s.i.g. and temperatures of 0100 C. for a time of 1-5 hours.

Catalytic systems which may be used include combinations of aluminumalkyl chlorides such as aluminum diethyl monochloride with trial-kylvanadates, exemplified by triisobutyl vanadate, or ethyl aluminumsesquichloride (Al (C H Cl Other vanadates include tri-secondary butylvanadate or mixed isopropyl secondary butyl vanadates.

The density of the copolymers may be varied over a considerable range,usually between about 0.84 to about 1.0, low density copolymers beingregarded as those having densities in the order of 0.84 to about 0.91and high- TABLE IIL-PROPERTIES OF ETHYLENE=VINYL ACETATE COPOLYMERS I AB 0 D E F G H I J Weight Percent Vinyl Acet te 27-29 27-29 27-29 27-2927-29 24-26 24-26 24-26 17-19 17-10 Cr/Vlnyl Acetate Mole Ratio 8/1 8/18/1 8/1 8/1 10 1 10 1 10 1 14 1 14/1 Melt Index, g./l0 mm 340470 -17522-2s -18 5-7 335-405 16-22 1. (3-2. 4 125-175 2. 1-2. 0 InherentViscosity 0 25 g [100 ml. Toluene at 30 om, 0,59 0. 63 0.78 0.85 0. 940.54 0. s4 1. 05 0. 54 0.98 Softening Point 250 280 310 100 280 370 210390 Tensile Strength, p.s.i 500 550 1, 000 2,000 2, 900 400 1. 700 2,700 850 2, 750 Elongation at Break, P 800 1,000 700 750 950 800 1.000 1,000 550 850 Density, g./ce 0. 95 0. 95 0. 95 0. 95 0. 95 0. 95 0. 95 0.95 0, 94 0, 04 The ethylene-propylene copolymers which are used indensity materials being regarded as those having densities the inventionconslst of certain polymers having the genfrom the latter upper limit toabout 1.0. Advantages are eral linear configuration gained by thecombination of several different degrees of H high and low density and/or high and low molecular (CHZ) 70 weight insofar as increase inlow-temperature properties Without a corresponding increase inbrittleness being experienced.

The waxes which may be used in the invention are petroleum waxesreferred to in the art as parafiin wax or as microcrystalline wax.Microcrystalline wax is also known as amorphous wax and is obtained bythe dewaxing of residual lubricating oils while the parafiin waxes areusually obtained by the dewaxing of distillate lubricating oilfractions. Distillate paraffin waxes usually having melting pointsbetween about F. and about 185 F., preferably between about and 165 F.Microcrystalline waxes which contain only minor amounts of normalparafiins .and largely predominate in highly branched and naphthenicwaxes have melting points in the order of 180 F.

The higher melting point parafiin waxes are especially useful in manycoating wax compositions: heavy distillate waxes obtained from thehighest boiling distillate lubricating oil fractions by dewaxing havemelting points in the order of and F., as does the high melting pointparaffin wax split from microcrystalline wax by fractionalcrystallization.

Special waxes may be obtained in particular instances, such as theplastic wax obtained by the deoiling of soft wax fractions whichnormally are separated from paraffin waxes during deoiling and dewaxingprocedures. These plastic waxes are useful for their extreme flexibilityand, while useful for this particular property, are especially subjectto being fortified with respect to blocking and tensile strength as wellas toughness by incorporation with the subject copolymers.

It is normal experience in designing wax coating compositions to find itnecessary to combine several waxes together in a single composition. Thepurpose of this, of

course, is to obtain the beneficial properties inherent in 30 eachparticular type of wax or to minimize adverse properties of other waxesso included.

I claim as my invention:

1. An improved heat-sealable petroleum wax coating composition, having aviscosity of at least 6000 centipoises at 300 F., of 87% weight ofpetroleum wax, 6.5% weight of a copolymer of ethylene and propylenecontaining 8593 mol percent ethylene units and having an intrinsicviscosity of 3.5 and 6.5% weight of ethylene-vinyl acetate copolymerhaving a molecular weight of between 25,000 and 90,000 and containingethylene and vinyl acetate units in a mol ratio of from 8:1 to 14:1.

References Cited UNITED STATES PATENTS 2,877,196 3/1959 Reding.3,146,214 8/1964 Jakaitis et al. 3,157,610 11/ 1964 Richardson.3,181,765 5/1965 Bonzagni et al. 3,189,573 6/1965 Oken. 3,205,186 9/1965Zaayenga. 3,210,305 10/1965 Coenen et al. 3,227,669 l/ 1966 Sauer.3,294,722 12/1966 Apikos et .al. 3,303,150 2/1967 Coenen et al.

FOREIGN PATENTS 634,016 12/ 1963 Belgium. 1,386,678 12/1964 France.1,389,415 1/1965 France.

MORRIS LIEBMAN, Primary Examiner.

B. A. AMERNICK, Assistant Examiner.

